Synergy of electromagnetic effects and thermophysical properties of metals in the formation of laser-induced periodic surface structures

Abstract

Femtosecond (fs) pulsed lasers have been widely used over the past few decades for precise materials structuring at the micro- and nano-scales. However, in order to realize efficient material processing and account for the formation of laser-induced periodic surface structures (LIPSS), it is very important to understand the fundamental laser–matter interaction processes. A significant contribution to the LIPSS profile appears to originate from the electromagnetic fingerprint of the laser source. In this work, we follow a systematic approach to predict the pulse-by-pulse formation of LIPSS on metals due to the development of a spatially periodic energy deposition that results from the interference of electromagnetic far fields on a non-flat surface profile. On the other hand, we demonstrate that the induced electromagnetic effects alone are not sufficient to allow the formation of LIPSS, therefore we emphasize the crucial role of electron diffusion and electron–phonon coupling on the formation of stable periodic structures. Gold (Au) and stainless steel (SS) are considered as two materials to test the theoretical model while simulation results appear to confirm the experimental results that, unlike with Au, fabrication of pronounced LIPSS on SS is feasible.